Eye tracking is a technique used to determine where a person is looking. In brief, the movements of a subject's eyes are tracked while the subject is presented with various visual media. Further information may also be gleaned from observing and quantifying other movements and changes in the pupils as the subject observes specific sub-aspects of a visual stimulus.
Test stimuli are images or other media that may be presented to test subjects for the purposes of gauging subject interest in one or more aspects of a stimulus. Various techniques exist for identifying a specific region or regions of a given test stimulus that attract attention from a subject viewing it. Advertisers, web page designers, and other creators of marketable content may use test stimuli with one or more test subjects to improve visibility of a desired brand or product placement, or to test the impacts of different media layouts on the emotional response of those viewing them.